Unable to change colours of objects in Illustrator

As you can see, here's one example of one object I'm unable to change to colour. 

I've changed the color options from "grayscale" to "CMYK", to choose what colors I want but when I select the desired color nothing happens.
I've selected the object and expand, and still nothing happens.

I've reset the settings to default and redo the above steps but nothing happens.

Anyone have this issue before?